This invention relates generally to forming a high density body from a powder material and more particularly to the forming of fully dense high speed steel bodies from metal alloyed powders and forming dense fully compacted bodies from ceramic powders. Thus the invention relates to forming a high density body from a powder material of metallic and non-metallic compositions and combinations thereof.
It is known to form fully dense high speed steel alloy bodies from hot worked billets of the steel which have been formed from the alloyed powder. Such a product is shown in U.S. Pat. No. 4,576,642 dated Mar. 18, 1986. It is also well known to anneal and cold compact to shape water atomized powders and then vacuum sinter the preformed powders to high density. U.S. Pat. No. 4,428,906 shows encapsulated preform bodies cast into a mold comprised of a pressure transmitting medium which consists of a rigid interconnected ceramic skeleton structure and a fluidizing glass. In such cases, the bodies must be encapsulated to prevent the binders and other volatile components of the ceramic material from contaminating the bodies. Also, U.S. Pat. No. 4,656,002 is a further illustration of the use of molten glass and the ceramic skeleton for consolidating a dense body of powder material of metallic or non-metallic compositions.
However, none of the prior art utilizes heat and pressure directly on the preform product and in a self-encapsulating environment to produce a high density body from a powder material of metallic and non-metallic compositions and combinations thereof which is uniform in three mutually perpendicular planes and which exhibit improved properties of machineability, and long service life.
Furthermore, in the high density bodies formed pursuant to prior art processes, the sulfides, such as manganese sulfide, always end up in a form approaching stringers extending lengthwise of the bodies. In the articles formed according to this invention, the sulfide particles are uniformly dispersed as small roundish pieces that are not oriented in any particular planes. The result is articles with improved machinability and grindability qualities.